core: Keep GDataClientLoginAuthorizer alive while notifying property changes
core: Keep GDataClientLoginAuthorizer alive while notifying property changes

It's possible for the GDataClientLoginAuthorizer to be finalised after
scheduling property notifications to happen in an idle function, but before
the idle function is called. This would cause crashes, so we hold a reference
to the authorizer while waiting for the idle function to be called.

Pecisk/libgdata,GNOME/libgdata,Pecisk/libgdata-gtasks,Distrotech/libgdata,Pecisk/libgdata-gtasks,pwithnall/libgdata,Pecisk/libgdata,Pecisk/libgdata,Pecisk/libgdata-gtasks,Distrotech/libgdata,Distrotech/libgdata,pwithnall/libgdata